However, for the time being, you might want use my KiCAD library. It has a Omega2S footprint which I could already test to some degree (manual soldering on one prototype board - I had access to an early Omega2S sample).

So that footprint should be fine, but of course, it's not official and there can always be details… Just create a PR on github if you have improvements…

Onion just released a .dxf drawing for the Omega2S footprint, and a .pcb file presumably containing a footprint (but not in KiCAD format), see here.

Comparing the .dxf with my Omega2S footprint (which I designed for manual soldering), the pads are smaller and reach a bit more under the Omega2S. This requires extremely precise placement because of the very close proximity of the non-masked shield housing contacts to pins C24/B24. If the part is only a fraction of a mm shifted right or left, C24 or B24 gets shorted to GND (shorting C24/XTAL_FREQ_SEL is particularily interesting, because then the Omega starts up, but with a wrong frequency, so console has a weird baud rate, and everything else depending on timing does not work. That's how I learnt to pay attention to these pads...)

So I think the official footprint is probably ok for automatic placement, but mine is safer for hand-soldered prototypes.